Traditionally, asphalt pavements are composite structures made of aggregates coated with a bituminous binder deposited onto a thickness of a few millimeters. After some time, these coatings undergo an ageing process due to the various stresses resulting from the road traffic and from the climatic conditions. This leads to a hardening of the binder, crack occurrences and/or to rutting phenomena.
A pavement treatment should therefore be foreseen to remedy such degradations. To this end, various recycling or renovating methods have been developed. The traditional recycling of pavement materials employs a wide range of adapted techniques, especially suitable to bituminous mixes. These multiple methods, which have been developed by road construction companies use specific equipments for a post-recycling in a dedicated plant or directly in situ. As regards bituminous materials, the principle upon which rehabilitation or recycling are based is directed to the regeneration of the bitumen that is present in the layer to be rejuvenated.
Indeed, the objective to aim at consists in rejuvenating the aged bitumen in the bituminous binder, the hardening of which is the consequence of the volatilization of the lightest fractions thereof. The regeneration process enables to correct the chemical constitution of the aged bitumen by means of a suitable binder so as to obtain a final binder possessing the characteristics of a traditional bitumen.
For this purpose, rejuvenating agents or binders are used since many years. The major part of the commercially available products is composed of petrochemicals based on fossil oils essentially made of naphthenic and aromatic molecules. Yet, these molecules comprise polycycloaromatic compounds (PCA) that are suspected of being carcinogenic and dangerous to the health and to the environment. Besides, some PCA-free oil molecules or vegetable-oil derived molecules like biodiesel are used sometimes. In addition, these compounds may be leached and carried along into the water tables and into the soil, thus contaminating the aquatic environment and the soils. Therefore, the use of such oils is forbidden because they are detrimental to the operator's health. In addition, they generally cannot be employed without supplying some new fresh bitumen as a supplement.
Rejuvenating binders comprising vegetable oils are also known, such as those described in the application GB 2462371. The application WO 2008/084014 also describes rejuvenating compositions comprising bitumen and palm oil.
However, rejuvenating binders based on crude oils or on vegetable oils as a drawback do give to surfaces onto which they are applied a slippery appearance because of their low reactivity.
There is therefore a need for developing new methods for recycling or for rejuvenating aged pavements by using rejuvenating binders which do not suffer from the drawbacks of the prior art.